The invention relates to a device for the homogeneous mixing of liquids flowing at different temperatures. Such liquid mixing problems are particularly encountered in nuclear power stations, which use a liquid metal as the heat transfer fluid. In this type of power station, part of the metal is removed from the main circuit and passed to a heat exchanger for cooling and then the thus cooled metal is reinjected into the main circuit. It is well known that mixing between the hot metals from the main circuit and the cooled metal is unsatisfactory and that there are temperature-based stratification zones in the main pipe.